Studies on the induction and expression of T cell-mediated immunity. XIV. Antigen-nonspecific oxidation-dependent cellular cytotoxicity (ODCC) mediated by sodium periodate oxidation of cytotoxic T lymphocytes

Alloimmune murine thymus-derived cytotoxic lymphocytes (CTL) generated in vivo or in vitro are shown to lyse antigen-nonspecific target cells (tumor cells, Con A, and LPS blasts) following treatment of CTL with an oxidizing agent, sodium periodate (NaIO4). It has been shown that NaIO4 oxidizes terminal sialic acid residues of cell surface macromolecules. The presence of reactive aldehyde groups, generated by NaIO4 modification, is required for the expression of antigen-nonspecific cytotoxicity because treatment of modified cells with a reducing agent such as potassium borohydride (KBH4) resulted in the abrogation of cytotoxicity. However, KBH4 treatment of unmodified or NaIO4-modified CTL has no effect on antigen-specific cytotoxicity. The modification of CTL by NaIO4 is sufficient to lead to the formation of lymphocyte-target cell conjugates and lysis of bound targets. Monoclonal antibodies directed against the Lyt-2 antigens of CTL, but not Lyt-1 antigens, in the absence of complement inhibited the nonspecific cytotoxicity resulting from NaIO4 modification of effector lymphocytes. These findings suggest that the mere interaction with or perturbation of appropriate cell surface molecule(s) of effector lymphocytes such as Lyt antigens by receptor-ligand interaction in SCMC or by NaIO4 modification in ODCC may lead to the expression of cytotoxicity. The present studies demonstrate a functional role of surface carbohydrates on CTL in cell-to-cell recognition and interactions. Furthermore, the results suggest that target cell modification is not a requisite for recognition and lysis in an antigen-nonspecific cytotoxic system such as ODCC. However, partial blocking of ODCC by alloantibodies directed against the H-2 of unmodified target cells suggests that NaIO4-modified CTL recognize unrelated target H-2 antigens. The implication of these findings on the molecular mechanism of cell-mediated cytotoxicity is discussed.     

Studies on the induction and expression of T-cell-mediated immunity. XIII. Membrane-associated antigens of cytotoxic T lymphocytes involved in cytotoxicity

An xenogeneic rat anti-mouse T-cell serum, designated RAT*, has been shown to block the cytolytic activity of cytotoxic T lymphocytes (CTL) at a postbinding step. RAT* serum or the IgG fraction was extensively absorbed with the target cell, P815, a DBA mastocytoma, and used with or without further absorption to immunoprecipitate specific molecules from radiolabeled membrane extracts of CTL derived from either in vivo-allosensitized mice or from cytotoxic clones maintained in in vitro cultures. Cell surface sialic acid residues were labeled by oxidation with sodium periodate (NaIO4) and reduction with tritiated sodium borohydride ([3H]NaBH4). Alternatively, cell surface proteins were labeled with 125I by lactoperoxidase-catalyzed iodination. Nonidet P-40 (NP-40)-solubilized radiolabeled membranes were then immunoprecipitated with RAT* serum and analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). Three membrane-associated molecules of 95,000, 140,000 and 180,000 Mr were found by such analysis. The sensitivity of these three molecules to trypsinization and their susceptibility to labeling with [3H]NaBH4 suggested that they are glycoproteins. Moreover, when RAT* serum or the IgG fraction was absorbed with various cell types, its ability to immunoprecipitate the three molecules correlated with its ability to block cytolysis. Adsorption of RAT* serum with CTL, but not with nonimmune thymocytes, significantly reduced the ability of RAT* serum to inhibit cytotoxicity and to immunoprecipitate the 95k, 140k, and 180k molecules. Thus, these findings suggest that one or more of these cell surface molecules of CTL may be involved in the cytolytic process.     

The proteolytic digestion of ox neurofilaments with trypsin and alpha-chymotrypsin.

Brief digestion of ox neurofilaments with trypsin liberates fragments that are soluble and have molecular weights ranging from 164 000 to 97 000. Peptide fingerprinting indicates that these regions, termed the tryptic head-regions, arise from the 205 000- and 158 000-mol.wt. components of the triplet. The remains of the parent polypeptides sediment with normal filaments and have been termed tail-regions. Digestion of neurofilaments with chymotrypsin also liberates soluble fragments (chymotryptic head-regions) but these have mol.wts. 171 000 and 119 000, though they too originate from the higher-molecular-weight triplet polypeptides. Tryptic and chymotryptic head-regions have extensive homology, and a low (less than or equal to 20%) helix content. Electron microscopy shows that chymotryptic digestion rapidly reduces the length of filaments, probably because this enzyme preferentially attacks the 72 000-mol.wt. polypeptide. In contrast, brief digestion with trypsin does not reduce filament length even though more than 90% of the two higher-molecular-weight components have been cleaved. These results indicate that the backbone of native filaments is formed from the 72 000-mol.wt. polypeptide together with the tail-regions from the 205 000- and 158 000-mol.wt. polypeptides. The corresponding head-regions of these components, which can represent nearly 75% of each molecule, are not necessary for preserving the backbone of native neurofilaments and are therefore good candidates for being the side arms that connect these filaments in nerve cells.     

Nucleoside Diphosphate-sugar 4-Epimerases I. Uridine Diphosphate Glucose 4-Epimerase of Wheat Germ

Uridine diphosphate (UDP)-glucose 4-epimerase (EC 5.1.3.2) has been purified over 1000-fold from extracts of wheat germ by MnCl₂ treatment, (NH₄)₂SO₄ fractionation, Sephadex column chromatography, and adsorption onto and elution from calcium phosphate gel. The enzyme has a pH optimum of 9.0. Km values are 0.1 mm for UDP-d-galactose and 0.2 mm for UDP-d-glucose. NAD is required for activity; K_a = 0.04 mm. NADH is an inhibitor strictly competitive with NAD; K_i = 2 μm. Wheat germ also contains UDP-l-arabinose 4-epimerase (EC 5.1.3.5) and thymidine diphosphate (TDP)-glucose 4-epimerase which are distinct from UDP-glucose 4-epimerase.     

胎盘型碱性磷酸酶的纯化及部分性质的研究

 <正> 胎盘型碱性磷酸酶(P-ALP)是碱性磷酸酶(EC3.1.3.1.ALP)的一种同工酶。P-ALP除出现于妊娠妇女血清外,一些学者还从恶性肿瘤患者血清中发现此酶,并证明它是一种特异性较强的肿瘤标志物。据此,建立P-ALP的简易纯化方法,制备纯度较高的酶制品是建立P-ALP灵敏的微量检测法的先决条件。本文报道以L-苯丙氨酸(L-phe)为配基,用氯代环氧丙烷活化Sepharose 4B的亲和层析法,从人胎盘纯化P-ALP,并对其部分性质进行了研究。     

The efficacy of biobehavioral and compliance interventions in the adjunctive treatment of mild pregnancy-induced hypertension

This investigation assessed the efficacy of a biobehavioral intervention in the adjunctive treatment of mild pregnancy-induced hypertension (PIH), a potentially serious complication of pregnancy in which normotensive women develop hypertension, proteinuria, and edema of unknown etiology late in gestation. Forty-five women with symptoms of PIH were randomly assigned to one of three treatment conditions: bed rest alone (the most common obstetrical treatment), bed rest with individualized compliance enhancement training, or a four-session biobehavioral treatment consisting of bed rest, compliance enhancement training, and individualized thermal biofeedback-assisted relaxation training. Results indicated that while blood pressure for the bed rest and compliance enhancement groups continued to rise and pose an increasing health risk to maternal and fetal well-being, subjects in the biobehavioral group maintained their blood pressure at a significantly lower, and presumably safer, level. The biobehavioral treatment is hypothesized to affect blood pressure levels in subjects with mild PIH through the mediation of the sympathetic nervous system, decreasing peripheral vascular resistance and cardiac output. The results of this investigation suggest that the biobehavioral intervention may be an effective adjunct to bed rest in the treatment of mild PIH remote from term.     

Breathing during sleep with mild hypoxia

To investigate ventilatory response to mild hypoxia during non-rapid-eye-movement sleep, we administered approximately 16% O2 (which corresponds to concentrations found in commercial high altitude air craft) to 12 normal subjects by using a Venturi mask, which did not alter the breathing pattern during this study. Under mild hypoxia, inspiratory minute ventilation during sleep showed an initial rapid increase (P less than 0.001) but then declined significantly (P less than 0.001) and stabilized. Stable levels differed among individuals and, compared with those measured before hypoxia, were significantly lower in some subjects, higher in one, and essentially unchanged in the others. The initial rapid increase in minute ventilation after mild hypoxia during sleep correlated with the respective values of hypoxic ventilatory response during the awake state (P less than 0.01), but the final lowered levels did not. We conclude that the ventilatory response after mild hypoxia during sleep is biphasic and hypoxic depression exerts considerable influence on ventilation under mild hypoxia during sleep. So we should take hypoxic depression into consideration to evaluate the response to hypoxia during sleep.